DESIGN OPTIMIZATION OF A BOGIE STRUCTURE FOR A TRADE-OFF BETWEEN PROCESSING TIME AND STRUCTUREAL PROPETY

초록

In the present railroad industry, weight reduction is the main issue in developing a vehicle structure. Train vehicle is composed of car body, wheel set and bogie system. Among them, bogie system has a great influence to a ride comfort by affecting vibration characteristics as well as reduction of power consumption through weight reduction. Korea Railroad Research Institute (KRRI) has developed a bogie system by autoclave molding process with composite material and obtained the satisfactory mechanical properties. Now, KRRI is in applying Resin Transfer Molding (RTM) process to improve productivity to manufacture a bogie system. Manufacturing process of bogie system by RTM process was analyzed numerically in the preliminary study. In RTM process, productivity or process time depends on the fiber volume fraction and inlet pressure as process condition. To control process time, thickness of a product can be considered as a design parameter to consider both of fiber volume fraction and inlet pressure. At this time, a final product weight can be varied according to thickness and mechanical properties of a final product also can be. Therefore, productivity, product weight and mechanical property are coupled together and simultaneous optimization should be considered to obtain a tradeoff between them. In this study, the optimal product design (thickness design) plan was suggested to consider processing time, weight and mechanical properties. RTM process for a bogie system was analyzed by ANSYS and a tendency of processing time depending on thickness was induced and mechanical properties were analyzed by ABAQUS. Based on the results of processing time and mechanical properties, optimization method can be proposed and applied to a simultaneous problem between process and structural properties.